When Labour won the election in May that year, the then health secretary Frank Dobson announced that all sports sponsorship by tobacco companies would be banned.

However six months later, the government announced that F1 would be exempt from the ban, prompting allegations that Mr Ecclestone's donation had influenced ministers - although this was strongly denied by the government.

Sir Sean Connery has criticised the ban on foreign donations

The BBC's political correspondent Shaun Ley said the changes would make it easier for voters to weigh up whether a large gift had affected policy.

"This is the area that it's not been possible to measure in the past.

"And it's been the most controversial area for the political parties because of that," he said.

The Tories have also had their share of controversy over the source of their funds.

Election limits

The British-born tycoon Lord Ashcroft has given large sums to the party despite being a tax exile, resident in Belize.

Foreign donations to UK parties are banned from Friday but for the next three months, that money can still be given directly to individual candidates.

The ban on overseas money has angered Sir Sean Connery who has donated large amounts to the Scottish Nationalist Party while living in the Bahamas.

Labour and the Conservatives will not be allowed to spend as much on the forthcoming election as they did in 1997.

At the last election the two parties each spent more than £25m. This time they will be allowed a budget of just £15m.

Spending limits for referendum campaigns mean only parties which receive more than 30% of the vote are allowed to spend the maximum £5m on their campaigns.